A Beautiful Day

October 22, 2008

Snapshot Quite a perfect day across the Pacific Northwest today.  Temps in the lower 70s at the beaches, near 70 here in town, and crystal clear blue skies the entire day.

East wind peaked around midday at the west end of the Gorge with a peak gust of 50 mph at Corbett.  The wind spread out and weakened quickly as it exited the Gorge.  All areas west of Troutdale had peak gusts below 40 mph, most areas not even above 30 mph.

The gradient is weakening this evening and I see at 10pm the wind at TTD is only 7mph.  A weak cold front is approaching and it'll turn flow onshore tomorrow.  A 2nd system gives us more extensive cloud cover on Friday.  That along with more low-level moisture probably means a pretty gray day.

We get "leftover" clouds Saturday morning, but then some good afternoon clearing.  Saturday night strong easterly flow commences once again.  That gives a day Sunday just like today.  Models all agree on strong ridging Sunday through Tuesday, then some sort of flatter flow returns the latter part of next week.  The 00z GFS has 500mb heights around 586dm Sunday afternoon through Monday morning.  It's going to be a slightly warmer airmass then what we had today…that's why we have lower 70s in the forecast for Monday…Mark Nelsen

By the Way: The annual What Will The Winter Be Like? Meeting is at OMSI 10am-Noon on Friday.  Anyone is welcome to attend.  If you enjoy hearing about weather patterns, winter, snow, and windstorms, this is for you.  Sponsored by OMSI and the American Meteorological Society.  I hope to meet some of you there.  Most of us on the weather team here at FOX12 will be there!  Plus many of the other local tv (and past tv) weather people show up too.


October 21, 2008

Snapshot Looks like easterly gradient is picking up quickly this evening as high pressure settles east of the mountains.  Still looks like maybe 8 millibars from PDX-DLS by mid-morning tomorrow.  Obviously fog is close to developing with a low temp-dewpoint spread at this hour.  This fog should be quite shallow with easterly wind developing just above the surface just about everywhere in the metro area by daybreak.  I think the increasing wind will also keep us fog-free east of I-205 tonight.

This won't be one of those wintertime events where the wind sticks around for days and days.  A front passing by to the north Thursday lowers pressures to the east pretty quickly then, killing the wind.

Long range?  There seems to be a tendency in several different models to want to bring troughing over the Pacific Northwest, a pattern similar to last winter.  00z GFS looks quite a bit different though.  It IS a safe bet that mild and warm weather continues at least through next Tuesday.  Beyond that though you should just roll the dice.  Mark Nelsen


October 21, 2008

Snapshot Looks like easterly gradient is picking up quickly this evening as high pressure settles east of the mountains.  Still looks like maybe 8 millibars from PDX-DLS by mid-morning tomorrow.  Obviously fog is close to developing with a low temp-dewpoint spread at this hour.  This fog should be quite shallow with easterly wind developing just above the surface just about everywhere in the metro area by daybreak.  I think the increasing wind will also keep us fog-free east of I-205 tonight.

This won't be one of those wintertime events where the wind sticks around for days and days.  A front passing by to the north Thursday lowers pressures to the east pretty quickly then, killing the wind.

Long range?  There seems to be a tendency in several different models to want to bring troughing over the Pacific Northwest, a pattern similar to last winter.  00z GFS looks quite a bit different though.  It IS a safe bet that mild and warm weather continues at least through next Tuesday.  Beyond that though you should just roll the dice.  Mark Nelsen


Dry Outlook

October 20, 2008

Snapshot  The big story as I return from some vacation time this evening is the dry and mild looking weather maps over the next 7+ days.  Hard to find much of any rainfall as we head towards the end of October.  Yet this is the time of year that rainfall really starts to pickup.  The last week of October and 1st week of November generally sees a tremendous increase in rainfall most years as we plunge quickly in the rainy season.  November is only slightly drier than December, making it the 2nd wettest month of the year here in Portland.  But basically November, December, and January are the 3 "big" months for rainfall.  By February the heavy rains of late Fall through early winter are fading a bit, interspersed with a few dry spells, making it somewhat drier than the other 3 months.

Not this year though…some sort of upper level ridging should sit near the West Coast over the next week or so.  This will add to the very nice (boring for the wx geeks) Fall we've had so far.  I didn't do too much last week on my time off, but there was plenty of sunshine for hikes yard/garden work.  Couldn't ask for much more in mid October!

Surface high pressure develops overhead tonight and tomorrow, then shifts east of the Cascades quickly late tomorrow afternoon.  The easterly gradient across the Cascades (and through the Gorge) builds up dramatically by late evening.  We're into that time of year where an easterly wind can begin anytime of the day, not just in the late night and early morning hours.  So I think the wind will blow all night tomorrow night east of I-205 within a few miles of the Columbia River.  WRF-GFS peaks out around 8 millibars by Wednesday morning PDX-DLS.  That should give us the first 50-55 mph gusts of the season at the west end of the Gorge.  That'll take a few more leaves off the trees out there.  You'll gain a few leaves in you live in Beaverton!  Mark Nelsen


A Few Days Off

October 10, 2008

Snapshot Tonight should be the coldest night so far this season.  You can see that frost will be a bit earlier than normal for most places on this graphic.  The text is quite small on this one, so click on it to get a larger view.  The data comes from Oregon Climate Service and is from the 1971-2000 30-year average.  As I recall from WAY back in the 90s, the frost dates used to be a bit earlier.  I thought Hillsboro used to be in late October and PDX was more like November 8th or 2nd, or something along those lines.

Not a whole lot to talk about tonight.  A surge of very dry air has moved south, out of Canada and into Eastern Washington and Northeast Oregon.  Dewpoints crashed into the teens in E. Washington during the day with a gusty north and northeast wind.  That very dry air just nicked The Dalles late this afternoon.  Notice the "moist" west wind stopped for an hour or so before resuming.  Dewpoint dropped at the same time.  With a switch to light easterly flow tonight and tomorrow, I think we'll see dewpoints drop some here west of the Cascades tomorrow.  Maybe a bit closer to 30 instead of 40.  This should keep fog away the next two nights.

We left rain out of the 7 day forecast since there was no one specific system that is forecast by all models to move through the Pacific Northwest.  But definitely close calls on Tuesday and/or Thursday/Friday.  We'll see.  Other than that the weather looks very slow.  Rob Martin, our morning meteorologist may post a bit next week, so treat him like family!  Mark Nelsen


October 9, 2008

Snapshot An exciting weather night, at least for October 9th in the Pacific Northwest.  Snow has briefly closed Hwy. 20 at Santiam Pass this evening (a collision), and snow has fallen all the way down to Prineville, Redmond, and Bend.  Then we just got an email from Sandy in Rockaway saying she just observed marble-size hail in Rockaway! 

Looks like another batch of showers moving south through Western Washington right now, but the trend is towards dry as we head to sunrise.  I'm going to raise my low temp forecasts based on a bit more cloud cover and dewpoints remaining relatively high.  So now I think tomorrow night WILL be the coldest night of our early October "cold snap".

No changes to the extended forecast thinking…next week looks either dry or almost dry with longwave ridging and high 500mb heights over the region…Mark Nelsen


October 8, 2008

Snapshot A nice flow of cool polar maritime air is headed out of the Gulf of Alaska…into the Pacific Northwest.  A cold front is getting organized (slightly) around 130W right now.  It's actually more of a solid line of showers than a large area of solid precipitation.  This arrives over us mid-morning tomorrow.  The combination of the showers, cloud cover, and colder atmosphere arriving overhead should give us a very chilly day Thursday.  This is a "one-shot" deal for rainfall;  the rain is gone by tomorrow evening, replaced by a much drier northerly low-level flow.  This means more sunshine for Friday, and of course a chilly start Friday morning as well.

It still looks good for a frost most areas Friday night, at least for most areas that don't get frost tomorrow night.  Okay, I'll make a few predictions for lowest either Friday or Saturday morning:  HIO=27, PDX=34, VUO=30, TTD=32.  Anyone else want to take a stab at it?

We should get a pretty quick rebound of temps Saturday PM through Monday as 850mb temps rise and we get a little offshore flow.  Dry weather until at least Tuesday when westerly flow sags back down over the Pacific Northwest.  Right now next week's systems are looking pretty weak and nothing to write home about, although the Mark Nelsen Vacation Rule applies for next week.  Maybe a surprise storm?  Mark